If your not hearing your Performer tracks one of the first things to check is the MTP setup under the apple menu.  Go  to the apple menu-->MTP II Console 1.1 -->Windows--> then to cable routing.    You will want to see a computer icon in the center of the screen with 8 virtual cables connected on either side.
This ensures that each piece of gear is talking back and forth with the computer.

If your not hearing one specific track or if it goes silent or changes volume unexpectedly partway through a song, then you may have unwanted controller 7 volume data in your track.  Double click the track and look for the offendening
#7 data.  Or you may need to add a controller 7 value of around 80 or higher to bring the track back up to an audible level (it may have been turned down inside a piece of gear before you got to the station).

Some other possible causes to check are the on buttons above each track of the Pro Mix.  The virtual master fader to the far right, on the led screen of the W5 in Song mode.   If you are seeing level on the Pro Mix but not hearing it, check the volume of the headphone amp.